A conventional IGBT module has been known in which a main terminal and a control terminal, which are external lead terminals, are soldered onto a conductive pattern (circuit pattern) formed on an insulating substrate (referred hereinafter as “patterned insulating substrate”) (see Patent Document 1 below, for example). Patent Document 1 uses independent terminals as the external lead terminals. The independent terminals are not fixed to a resin case, wherein they are not insert-molded into a resin case. The independent terminals are electrically connected to external wiring by nut globes which are resin structures of nuts and nut receivers fitted together.
With the recent increase in the integration density of an IGBT module, the joint between the patterned insulating substrate and the external lead terminals of the package needs to be strong and reliable in the assembly of the IGBT module. In addition, the positions to dispose the external lead terminals of the package need to be precise when mounting the external lead terminals on the patterned insulating substrate. A configuration of a conventional IGBT module is now described with reference to FIG. 19.
FIG. 19 is a cross-sectional diagram showing the configurations of substantial parts of the conventional IGBT module with independent terminals. A main terminal 53 and a control terminal 54, which are the independent terminals, are soldered or welded to a patterned insulating substrate 52 which is fixedly attached onto a heat dissipating base 51. A resin case 55 is bonded to the rim of the heat dissipating base 51. The part of the heat dissipating base 51 that is near the patterned insulating substrate 52 is covered with the resin case 55. Openings 56, 57 are formed in this resin case 55, so that the main terminal 53 and the control terminal 54 are exposed to the outside of the resin case 55 through the openings 56, 57.
Patent Document 1: U.S. Pat. No. 6,597,585
A problem with the conventional IGBT module shown in FIG. 19 is that the control terminal 54 sinks into the resin case 55 when a compressive load is applied to the control terminal 54. In a case where the control terminal 54 is welded to the patterned insulating substrate 52 or the control terminal 54 is deformed very little, the patterned insulating substrate 52 can be damaged by a compressive load applied to the control terminal 54.
Another problem is that a tensile load applied to the control terminal 54 tears the joint between the control terminal 54 and the patterned insulating substrate 52, pulling the control terminal 54 out of the resin case 55. Because this conventional structure allows the control terminal 54 to move easily, it is difficult to highly accurately position and fix the control terminal 54 in the resin case 55. The control terminal 54 is deformed easily especially when the arm portion thereof is long, making an accurate positioning of the control terminal 54 more difficult.